Free rein vs. free reign

The usual spelling of the phrase meaning freedom to do as one pleases is free rein, not free reign. The latter is a common misspelling, and it almost makes sense given reign‘s meaning (i.e., the exercise of sovereign power). But free rein, an allusion to horseback riding, is the original form, and it is much more common in published texts. The OED lists instances of its use from as long ago as the 17th century.1 As the ngram below suggests, free reign is a much newer development.

This ngram graphs the use of both phrases in a large number of English-language texts published between 1800 and 2000:

Examples

Instances of free reign are easily found, especially where editors are absent—for example:

And really, what player doesn’t want to go all Simon Cowell on a teammate every now and then if given free reign? [MLB.com]

You can either give kids free reign with designing their play mat or set them up with a challenge. [Patch]

Incumbent political heads across the region are taking notice while the nervousness has given crude a free reign to head north. [MarketWatch]

But free rein, as used here, is the more common spelling:

One part of that pact has already been exposed as flawed, since it turns out that, given a free rein, banks sometimes blow themselves up. [The Economist]

It seems that advertising companies are given free rein to make the cleverest, funniest ads of the year specifically to air during this one football game. [Guardian]

Julia Gillard took the debate to a lower level before the election when she invited people to give their prejudices free rein. [Sydney Morning Herald]

The second part of this sergeant’s letter calls for yet another vow. It reminds us that war, by its nature, breeds corruption and gives free rein to abuses of all sorts. [The Nation]